The present invention relates to an apparatus for analyzing a liquid specimen such as blood. The apparatus has a sampling valve for aspirating and pushing the liquid specimen (sample) in cylindrical shape, removing it quantitatively, and treating and analyzing it as required, and more particularly to an apparatus for analyzing liquid specimen applicable to discrete tests capable of selecting only a specimen necessary for measurement (examination), and treatment by diluting or the like.
An apparatus for counting blood corpuscles such as erythrocytes, an apparatus for classifying leukocytes, and an apparatus for counting reticulocytes are well known. An apparatus combining these plural functions into one (multifunctional apparatus) is also known. In such multifunctional apparatus, results of measurements (examination) of multiple items can be obtained by a single sampling operation. Depending on the specimens, however, unnecessary items may be also measured, which means waste of sample and reagent.
To eliminate such waste, it is required to have a function for sampling only the necessary portion in each specimen, and taking into the apparatus for analysis (discrete test function). For example, in the field of biochemical examination, it depends on the sampling system in which only a necessary amount of sample is aspirated from the pipette, and this sample is discharged into a reaction vessel. This method is simple in structure, but poor in precision. It is particularly a problem when handling viscous samples such as blood. In the blood cell counting apparatus, therefore, the specimen is sampled by pushing out the specimen in cylindrical shape and removing it quantitatively by means of a sampling valve.
Referring now to FIG. 1 and FIG. 2, the construction and operation of a general sampling valve are explained briefly below. Usually, the sampling valve comprises two fixed elements 10, 14 and a movable element 12 held between the two fixed elements 10, 14. FIG. 1 and FIG. 2 show two states of the sampling valve. In FIG. 1, the sample flows in the direction of arrow A, that is, from a pipette 16 through a flow-in passage Q, a metering (measuring quantity) passage P1, and a flow-out passage R1, and fills up the metering passage P1 of the movable element 12 (which is called the first state). As the movable element 12 moves from the first state, it is changed to the state of FIG. 2 (which is called the second state), and the sample which filled up the metering passage P1 in the first state is pushed out, and is transferred outside the sampling valve, together with liquid such as a diluent, in the direction of arrow B from passage T2 to passage T1.
In the apparatus for analyzing specimen by sampling the specimen by means of a sampling valve, there has been a keen desire for realizing the discrete test (sampling only a necessary portion for each specimen, and analyzing).